The present invention relates to a clip for a sheet electrode useful for holding or pinching a sheet electrode which is designed to be adhered for example onto the surface of a living body (skin) for picking up bioelectric signals from the living body so as to deliver the bioelectric signals to an external device for the purpose of preparing an electrocardiogram or electromyogram.
In the measurement of bioelectric signals as in the case of preparing an electrocardiogram, a sheet electrode comprising a sheet-like conductive terminal having a conductive polymer gel layer attached to one surface thereof is employed in such a manner that it is adhered through the polymer gel layer onto a chest or other portions of an examinee at first, and after the conductive terminal of the sheet electrode is pinched with a clip, bioelectric signals from the examinee are picked up and delivered via a conductive wire connected with the clip to a measuring apparatus for the evaluation.
As for the sheet electrode clip to be employed for the aforementioned purpose, several kinds of the clip have been disclosed for instance in Japanese Utility Model Unexamined Publication H6-74103. As shown in this utility model publication, so-called alligator clip which is usually employed is accompanied with a problem that since the conductive terminal of the sheet electrode is formed of a thin and slippery metal sheet, the clip is likely to be disengaged from the terminal while the terminal is pinched with the clip, thus leading to the generation of trouble in the examination. When the force of spring is increased in order to prevent the clip from being disengaged, the manipulability in the engagement and disengagement of the clip would be deteriorated, thus inviting another problem.
In the light of these problems, there is proposed in the above-mentioned utility model publication an electrode clip having a protrusion at a tip end thereof, which is designed to be inserted into a through-hole formed at an end portion of the conductive terminal of sheet electrode. This electrode clip is advantageous in that the sheet electrode can be reliably held by the clip as the through-hole to be engaged with the clip is formed at one end portion of the conductive terminal of sheet electrode. However, this electrode clip is still accompanied with the problems that it is troublesome in manufactural viewpoint to form a through hole in the sheet electrode, and at the same time, since the sheet electrode is accompanied with an adhesive layer, it is difficult to completely remove the tailings of the punched hole.
Additionally, the urging force of the spring of the clip is set so as to always close the tip end portion of the clip which pinches the conductive terminal of the sheet electrode. Therefore, it is required, at the occasion of employment, to maintain an opened state of the clip as opposed to the urging force of the spring, thereby enabling the conductive terminal portion to be inserted into the clip. In the light of such an operation, it is not necessarily easy to insert the protrusion formed on the clip into the through-hole formed at one end portion of the conductive terminal.
In any case, the conventional clips require not only a conductive member to be connected with a conductive wire but also a spring member to provide the clip with an urging force, thus necessitating a relatively large number of parts, and moreover, the assembling thereof is not easy. Further, since the conductive wire and the conductive member are integrally molded through an insert molding, it would be difficult to expect a high yield in the manufacture thereof and due to a high thermal stress in the manufacture thereof, it would be difficult to avoid the molded product from being easily broken.
The aforementioned utility model publication also discloses another embodiment of the electrode clip wherein a movable member is mounted on a substrate in such a way that it is enabled to slide in relative to and in parallel with the substrate, and the movable member is allowed, due to the elasticity thereof, to move forward beyond a protrusion formed on the substrate. Since a spring member for generating an urging force is not employed in this embodiment, the number of parts can be reduced. However, it would be difficult to allow the movable member to smoothly move along the surface of conductive terminal which is mounted on the substrate through an engagement between a through-hole formed in the conductive terminal and a protrusion formed on the substrate. Moreover, the conductive terminal may possibly be curled up due to the movement of the movable member.
The present invention has been accomplished in view of the aforementioned problems, and therefore, an object of the present invention is to provide a clip for a sheet electrode, which is capable of easily pinching a sheet or film electrode (hereinafter referred to as a sheet electrode), capable of reliably pinching a sheet electrode without allowing the sheet electrode from being easily disengaged from the clip even if a conductive wire is pulled, capable of minimizing the number of parts so as to make the assembling thereof very simple, and capable of being stably used for a long period of time.
With a view to realize the aforementioned object, the present invention provides a clip for a sheet electrode, which comprises a substrate provided with supporting axes; a movable plate provided with slots which are adapted to engage with the supporting axes respectively; a leaf spring which is made of a conductive material, bent in the near middle thereof, i.e. U-shaped, interposed between the substrate and the movable plate, and connected with a conductive wire; wherein said leaf spring is always urged such that the fore-end portion thereof is kept in an open state; said movable plate is made pivotal in a direction to close the clip as opposed to the urging force of the leaf spring, thereby enabling a pair of distal ends of the leaf spring to contact with each other to pinch the sheet electrode therebetween; and said movable plate is enabled to shift forward along the slots while rendering the sheet electrode pinched between said pair of distal ends of the leaf spring and to rest while being kept engaged with the substrate. The clip can be also used for film electrode.
According to this clip for a sheet electrode, since the leaf spring is always urged such that the fore-end portion of the clip which is designed to hold a conductive terminal of sheet electrode is always kept in an open state, the sheet electrode can be easily introduced into the pinching portion of the clip. After the introduction of the sheet electrode into the pinching portion of the clip, the movable plate is pivoted in a downward direction as opposed to the urging force of the leaf spring, thereby enabling the conductive terminal of sheet electrode to be pinched and fixed from top and bottom by a pair of distal ends of the leaf spring which is made of a conductive material. While keeping this condition, the movable plate is then shifted forward so as to enable the movable plate to take a rested state mechanically. As a result, it is possible to prevent the sheet electrode from being disengaged even if an external force is inadvertently applied to the sheet electrode. When the movable plate is kept maintained in this state, the fore-end portion of the movable plate acts to cause the conductive terminal of the sheet electrode to press-contact with the distal end portion of the lower half of the leaf spring, thereby ensuring a reliable electric contact between the leaf spring and the conductive terminal of the sheet electrode.
When the sheet electrode is to be removed from the clip, the movable plate is pulled rearward from the rested position thereof. As a result, the engagement between the substrate and the movable plate can be easily released, and due to the force of the leaf spring, the movable plate is allowed to reliably return to the original opened state, thus allowing an easy removal of the sheet electrode.
According to this clip for a sheet electrode, since the leaf spring employed for giving an urging force is also functioned as a conductive member, it is no more required to provide additional conductive member for making a connection with the conductive wire. Further, since the leaf spring can be integrally formed with the conductive wire through fuse-bonding for instance, the resultant composite member being enabled to be assembled with the substrate, the number of parts can be minimized, thus facilitating the assembling thereof, and at the same time, it becomes possible to prevent the assembled body from being easily destroyed.
According to a preferable embodiment of the present invention, the movable plate is enabled, while the slot thereof is kept engaged with the supporting axes of the substrate, to pivot from the position where the fore-end portion of the movable plate is opened upward due to the urging force of the leaf spring to the position where the fore-end portion of the movable plate is further opened upward. Under this condition, the opened angle between the movable plate and the substrate can be enlarged, so that the assembling work such as the installation of the leaf spring onto the substrate can be facilitated.
According to a preferable embodiment of the present invention, the engagement between the movable plate and the substrate is effected through an engagement between a protrusion formed on the substrate and a cut-out groove formed in the movable plate. According to this mechanism of engagement, the manipulation to open and close the clip would become easy and at the same time, the engagement and disengagement of the sheet electrode can be reliably performed.
In a preferable embodiment of the present invention, both distal end portions of the leaf spring are provided with upright portions respectively, these upright portions being directed to face to each other. More preferably, at least one of these upright portions is provided at the tip end thereof with a large number of projected and recessed portions. When upright portions are formed in this manner, the engaged state of the conductive terminal portion of the sheet electrode can be further ensured, so that the sheet electrode can be reliably prevented from being inadvertently disengaged during the measurement operation using the sheet electrode.
According to another preferable embodiment of the present invention, the tip end portion of at least one of the halves of the leaf spring is provided with upright portions having different heights, and the tip end portion of the other of the halves of the leaf spring is provided with an upright portion which is designed to be inserted between said upright portions having different heights. When upright portions are formed in this manner, the conductive terminal portion of the sheet electrode can be pinched with said conductive terminal portion being bent accordingly. For example, the upright portion disposed on the movable plate side acts to push the conductive terminal portion of the sheet electrode into an interval between a pair of said upright portions disposed on the substrate side, thereby ensuring an excellent contact state, and at the same time, achieving a stable pinched and fixed state of said conductive terminal portion.
In another preferable embodiment of the present invention, said leaf spring is provided with a protruded portion for preventing the conductive terminal portion of the sheet electrode from excessively entering into the clip, thereby enabling the pinching position of the sheet electrode in the individual clip to be set to a fixed position, thus enabling to obtain a stable measurement value. By the way, this protruded portion may be formed perpendicular or be inclined rearward to the inserting direction of the sheet electrode in relative to the substrate under the condition where the sheet electrode is being pinched by the distal end portions of the leaf spring.
In another preferable embodiment of the present invention, said leaf spring is provided, at the portion facing the substrate, with an opening, and said substrate is provided with a projected portion which is designed to be engaged with the opening. When an opening and a projected portion are formed in this manner, the engagement of the leaf spring to the substrate can be further stabilized, so that the leaf spring can be reliably prevented from being inadvertently disengaged from the substrate.
In a further preferable embodiment of the present invention, a connecting portion between the leaf spring and the conductive wire is covered with a heat-shrinkable resin. When this connecting portion is covered with a heat-shrinkable resin, the stability of the connecting portion can be ensured, so that the connecting portion can be prevented from being inadvertently separated or from being exposed to a chemical.
By the way, the termxe2x80x9csheet electrodexe2x80x9d employed in the present invention should be construed to include not only an electrode or an earth electrode, which is designed to be adhered onto the surface of a living body (skin) for picking up bioelectric signals from the living body for the purpose of preparing an electrocardiogram or electromyogram, but also an electrode which can be employed for introducing, through a skin, an external electric signal (of low frequency, for instance) into the interior of a living body or an electrode which can be employed in the general industrial purpose. These electrodes generally comprise, as an insulating substrate, a film of synthetic resin such as polyethylene terephthalate (PET), polyethylene, polypropylene, polystyrene, polyvinyl chloride, etc.; and an electric insulating material such as a synthetic paper, unwoven fabric, etc. On this insulating substrate, an electrode element coated with a silver paste, a silver/silver chloride paste, a carbon paste, etc., or a conductive material such as a metal foil is laminated to act as a conductive terminal (electrode element). On the portions of these electrodes which are to be adhered onto a living body, a conductive material layer comprising a natural polymer type conductive material such as cross-linked karaya gum, or comprising a conductive polymer gel such as sodium polyacrylate, polyacryl amide, etc. can be laminated.